In general, an automobile is equipped with a wire harness (internal wirings) within the vehicle and the wire harness is used for feeding electricity to electrical equipments within the vehicle, communication and sensing, etc. Such wire harness is generally constituted of electric wires, protective members and terminals such as connectors which are mounted to the end portions of the electric wires. Conventionally, metal wires constituted mainly of copper are employed as the conductors of the electric wires.
In recent years, weight reduction of vehicular components has been advanced due to demands for fuel consumption reduction and a wire harness is no exception. Also, because of the necessity of resources saving and recycles, there is a need for reduction of the amount of copper used for electric wires.
There are two important characteristics required for electric wires. One of them is the electrical conductivity and the other is the tensile strength. Copper, which is often used for the conductors of electric wires of the aforementioned wire harness, is a metal material with a very low electrical resistance. Therefore, the electric wires which have the conductors made of copper can offer sufficient conductivities even when they have relatively small wire diameters. However, in order to maintain a tensile strength required for electric wires, the wire diameters must be made large to some degree. Consequently, there is the necessity of reducing the amount of copper used for electric wires while maintaining the tensile strength.
On the other hand, there are electric-wire conductors made of stainless steel wires with a copper layer on their outer circumferences (refer to, for example, Patent Document 1 and 2). Further, as electric-wire conductors consisting of different types of metal wires stranded together, there are stranded wires consisting of stainless steel wires and copper wires (refer to, for example, Patent Documents 3 and 4).
Patent Document 1: JP-A No. 1-283707
Patent Document 2: JP-B No. 7-31939
Patent Document 3: JP-B No. 63-23015
Patent Document 4: JP-A No. 1-225006